In the manufacture of free-machining steels containing lead, it is very difficult to obtain uniform lead distribution in the solidified steel product. The difficulty is primarily due to the lead having a higher density than molten steel, requiring thorough mixing of lead with the steel and causing rapid settling and segregation of the lead before steel solidification is complete. To minimize settling within the steel, lead has been added as close to the time of solidification as possible. In ingot practice, lead has been injected into the stream between the ladle and the mold. For continuous cast product, lead has been added directly to the mold as disclosed in U.S. Pat. No. 4,524,819 or in the tundish as in J 60103111, J 60127055, J 60103112, J 603113 and J 59113156. It is difficult to obtain uniform mixing when making the lead addition to the caster mold, while, on the other hand, segregation tends to occur when the addition is made to the tundish.
It is a primary object of this invention to provide a tundish of improved design for promoting mixing of lead with the molten metal therein and minimizing the degree of lead segregation prior to delivery of molten metal into the mold.
It is a further object of the invention to provide a process for mixing alloying elements with molten metal using the improved tundish just mentioned.